And suddenly, out of the blue, the Rosebud American Kitchen & Bar’s patio appeared and the Out of the Blue sign became a little less effective. The Davis Square diner closed in May and reopened Sept. 15 at 381 Summer St., Somerville, the old and new neighbor to the seafood restaurant. (The old version never had a patio.) The sign wasn’t so much Out of the Blue as it was out of space.